Spiral conveyor apparatus with automatic flow control

ABSTRACT

A spiral conveyor with automatic flow control includes a plurality of curved segments connected to form a spiral for the flow by gravity of articles from an upper level to a lower level. Each of the segments includes freely rotating skate wheels forming a conveying surface and a controlled, powered cylindrical roller. A sensor mounted in each segment senses the presence of an article in the segment. A controller receives the signals from the sensors and activates the associated roller for transport mode to assist articles through the conveyor if the path is clear, or if the downstream portion of the conveyor is blocked, to reverse the roller for accumulate mode to hold articles in the segment until the path is cleared.

BACKGROUND AND SUMMARY

[0001] The invention is directed to roller conveyor systems usinggravity to move articles from an upper level to a lower level. Moreparticularly, the present invention relates to a gravity powered spiralconveyor including means for assisting and controlling the movement ofarticles through the conveyor.

[0002] A conveyor in accordance of the invention provides an apparatusfor automatically transporting articles from one level to a lower levelor for accumulating articles in the conveyor based on article movementconditions. The conveyor of the invention can be used as part of alarger conveyor system and is readily adaptable for providing a range ofheight changes and direction changes. While the invention is preferablydirected to a spiral conveyor, the inventive principles may be appliedto other conveyor configurations, as will be appreciated by thoseskilled in the art, and the invention is not necessarily limited to theembodiments described below.

[0003] A conveyor in accordance with the invention includes a framepreferably defining a spiral conveying path from an upper level to alower level. A conveying surface is provided by a plurality of freelyrotatable rollers or skate wheels. A plurality of controllable,reversible powered rollers are individually disposed in the frame atpredetermined intervals along the conveying path. Sensing means ismounted in the frame to detect the presence of conveyed articlesadjacent each of the powered rollers. The powered rollers arecontrollable for assisting the gravity transport of the articles or forreversed rotation for accumulating articles in the conveyor when thedownstream portion of the conveyor is full. Accumulate mode preventsarticles from overloading the lower end of the conveyor when transportfrom the conveyor is blocked by holding the articles in the conveyor.This facilitates resumption of transport when the blocked condition isresolved.

[0004] According to the invention, a spiral conveyor includes aplurality of curved segments fastened to form a spiral path, each havinga predetermined cant. The curvature and the cant of the segments can beselected so that the spiral executes a desired number of turns for aselected height change.

[0005] In accordance with a preferred embodiment of the invention, eachof the segments is shaped to define a 90° arc which simplifiesmanufacturing and assembly. The 90° segment arcs provide a convenientsize for the transport and accumulate modes of operation. In addition,90° arcs allow the entry segment and exit segment to be oriented at aconvenient parallel or perpendicular direction to accommodate thedirections of the feed and takeaway conveyors.

[0006] According to another aspect of the invention, a powered roller isincluded in each of the segments to control the movement of a conveyedarticle through the segment. The powered rollers are controllable torotate alternatively in a forward direction to assist the transport ofarticles down the conveyor or a reverse direction to accumulate articlesin the conveyor.

[0007] According to yet another aspect of the invention, sensing meansis included to sense the presence of an article in each of the segments.A signal from the sensing means is used to control the powered rollers.Preferably, the sensing means comprises a plurality of sensors mountedin the conveyor with one sensor in each segment. The sensing means canbe any suitable device, for example, a photocell or a mechanical switch.

[0008] A control means receives the signals from the sensing means anduses the signal to determine whether to activate the powered rollers fortransport mode or accumulate mode depending on a comparison of thepresence of articles in adjacent segments, that is, whether a downstreamsegment is clear to receive an article from the segment immediatelyupstream.

[0009] The control means operates in transport mode to activate a rollerto rotate in a forward direction in a segment when the sensing meanssenses the presence of the article in the segment and senses that thedownstream adjacent segment is clear.

[0010] In transport mode, the rollers rotate at a set speed in adirection for forward movement of the articles. Thus, articles of lightweight that may have difficulty overcoming inertial or frictional forceson the conveyor are accelerated, and heavier articles that may move toofast for the takeaway conveyor to handle smoothly are slowed down byfriction produced in moving across the powered roller.

[0011] The control means operates in an accumulate mode upon sensingthat an article has remained in a segment for a predetermined length oftime. When accumulate mode is activated, the control means activates therollers in that segment to rotate in reverse to hold the article in thesegment, and as an article is sensed in the immediately upstreamsegment, that roller is rotated in reverse. The control means continuesto activate the segments in reverse sequence as long as a downstreamblockage exists. When the downstream segment clears, the control meansreverts to transport mode and activates the segments to resume movingarticles forward in the same order in which they were set in accumulatemode.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The invention will be better understood through the followingdetailed description in conjunction with the appended drawings, inwhich:

[0013]FIG. 1 is a schematic representation of a front view of a spiralconveyor in accordance with the invention;

[0014]FIG. 2 is a top view of the spiral conveyor of FIG. 1; and

[0015]FIG. 3 is a view of a conveyor segment in accordance with theinvention.

DETAILED DESCRIPTION

[0016] A conveyor system according to the invention is shownschematically in FIG. 1. The conveyor system 20 comprises a base 22 anda conveyor frame 30 supported on the base. The conveyor frame 30 isformed as a spiral descending from an upper entry level 32 to a lowerexit level 34. The conveyor frame 30 includes roller devices providing aconveying surface to allow an article 15 entering the conveyor frame 30to travel by force of gravity from the entry level 32 to the exit level34. The spiral conveyor system 20 can be connected to a larger conveyorsystem having a feed conveyor 12 to deliver articles to the spiralconveyor 20 and a takeaway conveyor 14 to transport articles from thespiral conveyor to a downstream conveyor.

[0017] As seen in FIG. 2, the conveyor 30 according to the invention isassembled from a plurality of curved segments 40 a, 40 b, 40 c, and soon, mounted together on the base 22 to form the spiral conveyor frame30. According to a preferred embodiment, the segments are shaped to havea uniform, predetermined downward cant, which allows the segments to beconveniently joined to form a spiral spanning a desired height. Inaddition, the arcs preferably are formed as 90° arcs.

[0018] The cant can be selected so that the spiral provides a desirednumber of full or part turns for a given height change. The 90° turn ofthe segments permits the entry and exit levels to be mutually orientedat any parallel or perpendicular direction. For example, if a feedconveyor 12 having a direction A, as indicated by the arrow in FIG. 2,is connected to segment 40 a, a takeaway conveyor can be connected,after an appropriate number of intervening segments for a desired heightchange, at a desired exit direction parallel C or E, or perpendicular Bor D, to the feed conveyor 12 direction.

[0019] Conveyor segment arcs of 90° are convenient for manufacture andassembly, however, the segments 40 may be formed as other than 90° arcs,as is convenient for the particular installation, and the invention isnot limited to the embodiment described.

[0020]FIG. 3 illustrates in a highly simplified form a conveyor segment40 in accordance with the invention. The arrows indicate the directionof travel for articles on the segment 40. The segment 40 includes achassis 42 supporting a plurality of roller devices 44. The rollerdevices 44 can be skate wheels, as illustrated, or can be roller balls,cylindrical rollers, or other suitable devices.

[0021] Each segment 40 also includes a powered roller 50. The poweredroller 50 can be rotated alternatively in a direction to correspond witha forward travel direction of the segment, or in a reverse direction toresist forward movement. Powered, reversible rollers suitable for theapparatus according to the invention are available from several rollermanufacturers, for example, the Interroll Model 8.220P44D15 is one suchsuitable roller. The powered rollers 50 are provided with an outercoating of PVC to provide a suitable friction surface. The rollers 50rotate at a set speed and will add thrust to speed up slower moving,light weight articles and will drag on faster moving, heavier articlesto slow them, and will thus help make the flow of articles more uniform.

[0022] The powered roller 50 may be located at any convenient place onthe segment. For reasons of manufacturing convenience, the roller 50 ispreferably mounted at the exit end 46 of the segment. However, theroller can be positioned anywhere in the segment.

[0023] Each segment also includes a sensor 52 mounted on the chassis 42upstream of the powered roller 50. The sensor 52 detects the presence ofa conveyed article in the segment before it reaches the roller 50 andsends a signal to a controller 60, described below, for activating theroller. The sensor 52 is located a sufficient distance from the poweredroller 52 to allow the controller 60 to receive a signal from the sensorand to activate the roller to be rotating as the article reaches theroller. Preferably, the sensor 52 is positioned at about the midpoint oftravel of the segment. Alternatively, the sensor could be placed at anylocation upstream of the powered roller, and the controller 60 could beprogrammed to take into account the distance, if necessary.

[0024] According to a preferred embodiment of the invention, the sensor52 is a photoelectric device having a light source and a photocell, asillustrated. Other sensing devices may be used, for example, amechanical switch having a leaf interposed in the conveying path.

[0025] The controller 60 is a programmable microprocessor that isconnected to receive signals from each of the sensors 52 and, using thatinformation, to control the powered rollers 50 for either a transportmode or an accumulate mode.

[0026] According to a programmed operational method in accordance withthe invention, the controller 60 receives a signal from a sensor Nindicating that an article is present in segment N, where “N” indicatesany segment in the spiral conveyor. The controller 60 then checks thecondition of sensor N+1 in segment N+1 immediately downstream of segmentN (for the exit segment, the term “N+1” indicates a takeaway conveyorconnected at the exit segment). If sensor N+1 is clear, the controller60 activates roller N to rotate in a forward direction, whichcorresponds to transport mode. If sensor N+1 indicates an articlepresent, the controller checks for how long the sensor N+1 has indicatedthe presence of the article. If the duration of the “article present”signal from sensor N+1 is more than a predetermined time, the controlleractivates roller N to rotate in reverse to prevent the article insegment N from traveling to segment N+1. Subsequently, when the sensorN+1 indicates the segment is clear, the controller activates the rollerN to rotate in the forward transport direction and transport moderesumes.

[0027] When operating in transport mode, the controller coordinates therotation of the rollers to facilitate the movement of articles throughthe conveyor. As an article enters the spiral conveyor and is sensed bythe first sensor in the first segment, the controller determines whetherthe next downstream segment is clear. If so, the controller then startsthe first roller in forward, transport rotation. After the articlespasses the first roller, the first sensor senses that the article haspassed, and the controller turns the first roller off and starts thesecond roller in the second segment. As the article passes the secondroller and second sensor, the controller turns off the second roller andactivates the third roller in the third segment. This operationcontinues until the article passes the bottom segment. The system workscontinuously and will operate simultaneously for articles as they enterand travel through the various segments.

[0028] Accumulate mode will usually be initiated by a blocked conditionat the exit conveyor segment 34. The controller will first activate theexit conveyor roller to rotate for accumulating articles, and willactivate segments sequentially, up to the entry conveyor if necessary.By way of example, the exit conveyor can become blocked because of acondition at the takeaway conveyor 14 causing a backlog of articles. Thecontroller will activate the exit roller to rotate in reverse toaccumulate articles if the sensor at the exit conveyor senses thepresence of an article for predetermined time duration. The timeduration is sufficiently long to determine that an article has actuallystopped at the sensor (and is not merely slow moving), and a duration inthe range of about 2 to 5 seconds has been found to be suitable. Thetime duration can be adjusted for the size and normal transport speed ofthe articles in the conveyor.

[0029] Depending on the size of the articles, the exit segment (and ofcourse, each of the other segments) can accumulate at least one, andusually several articles. The accumulation of articles in the exitsegment will eventually cause an article to stall in the precedingsegment, thus blocking the preceding sensor. A signal from thispreceding sensor to the controller indicating the presence of an articlefor more than the predetermined time will cause the controller toactivate reverse rotation of the associated roller, and accumulationwill occur in this segment. The change to accumulation mode continuesupward through the conveyor as each segment senses the presence withoutmovement of the articles.

[0030] When the controller receives a signal that the takeaway conveyoris clear, the roller in the exit conveyor is changed to rotate fortransport, and the previously accumulated articles are transported tothe takeaway conveyor. The sensor in the exit conveyor will thenindicate that the exit conveyor is clear, and the controller will thenchange the next upstream roller to rotate in transport mode, thusreleasing articles from that segment, and so on up to the entry segment.

[0031] The controller can be programmed to determine whether the clearsignal from a sensor has a predetermined duration, for example 2seconds, to avoid changing to transport mode for simple shifts orslippage of the articles in the exit conveyor.

[0032] It will be understood that Applicants' invention is not limitedto the particular embodiments that have been described and illustrated.This application contemplates any and all modifications that fall withinthe spirit and scope of Applicants' invention as defined by thefollowing claims.

What is claimed is:
 1. A spiral conveyor apparatus, comprising: aplurality of conveyor segments arranged as a spiral, including at leastan entry segment at a first level and an exit segment at a second level,each conveyor segment having a plurality of freely rotatable rollerdevices forming a conveying surface; a powered roller mounted in eachsegment, each powered roller being individually powered and individuallycontrollable for selected rotation; means for sensing a conveyed articlein each conveyor segment; and means for receiving signals from thesensing means and responsively controlling the powered rollers in atransport mode for transport of articles and in an accumulate mode foraccumulation of articles.
 2. The apparatus as claimed in claim 1 ,wherein said means for controlling the powered rollers is configured toactivate a roller in a segment in the transport mode upon receiving asignal that an article is sensed in the segment and receiving a signalthat a segment immediately downstream of the subject segment is clear totransport articles.
 3. The apparatus as claimed in claim 1 , whereinsaid means for controlling the powered rollers is configured to controla roller in a segment in the accumulation mode upon receiving a signalthat an article is sensed in the segment and receiving a signal that anadditional article has been present in a segment immediately downstreamof the subject segment for a predetermnined time duration.
 4. Theapparatus as claimed in claim 3 , wherein the predetermined timeduration is at least two seconds.
 5. The apparatus as claimed in claim 1, wherein said means for sensing the conveyed articles includes aplurality of sensing devices, one device positioned at each conveyorsegment upstream of the powered roller.
 6. The apparatus as claimed inclaim 5 , wherein the sensing devices are photocell devices.
 7. Theapparatus as claimed in claim 1 , wherein each conveyor segment definesan arc of at least 45°.
 8. The apparatus as claimed in claim 1 , whereineach conveyor segment defines an arc of at least 90°.
 9. The apparatusas claimed in claim 1 , further comprising a takeaway conveyor connectedto receive conveyed articles from the exit segment and means for sensingconveyed articles in the takeaway conveyor.
 10. The apparatus as claimedin claim 1 , wherein said means for controlling the powered rollers isconfigured to activate the accumulate mode upon receiving a signalindicating an article in an exit segment for at least a predeterminedlength of time, wherein said means for controlling the powered rollersincludes means for activating the powered rollers to rotate in reverseto maintain the article in the exit segment.
 11. A spiral conveyorapparatus, comprising: a plurality of conveyor segments arranged as aspiral, including at least an entry segment at a first level and an exitsegment at a second level, each conveyor segment having a plurality offreely rotatable roller devices forming a conveying surface; a poweredroller mounted in each segment, the powered roller being individuallypowered and individually controllable for selected rotation; means forsensing a conveyed article in the conveyor segment; and means forreceiving signals from the sensing means and responsively controllingthe powered rollers in a transport mode for transport of articles and inan accumulate mode for accumulation of articles.
 12. The apparatus asclaimed in claim 11 , wherein said means for controlling the poweredrollers is configured to activate a roller in a segment in the transportmode upon receiving a signal that an article is sensed in the segmentand receiving a signal that a segment immediately downstream of thesubject segment is clear to transport articles.
 13. The apparatus asclaimed in claim 11 , wherein said means for controlling the poweredrollers is configured to controller a roller in a segment in theaccumulation mode upon receiving a signal that an article is sensed inthe segment and receiving a signal that an additional article has beenpresent in a segment immediately downstream of the subject segment for apredetermined time duration.
 14. The apparatus as claimed in claim 13 ,wherein the predetermined time duration is at least two seconds.
 15. Theapparatus as claimed in claim 11 , wherein said means for sensing theconveyed articles includes a plurality of sensing devices, one devicepositioned at each conveyor segment upstream of the powered roller. 16.The apparatus as claimed in claim 15 , wherein the sensing devices arephotocell devices.
 17. The apparatus as claimed in claim 11 , whereineach conveyor segment defines an are of at least 45°.
 18. The apparatusas claimed in claim 17 , wherein each conveyor segment defines an arc ofat least 90°.
 19. The apparatus as claimed in claim 11 , furthercomprising a takeaway conveyor connected to receive conveyed articlesfrom the exit segment and means for sensing conveyed articles in thetakeaway conveyor.
 20. The apparatus as claimed in claim 11 , whereinsaid means for controlling the powered rollers is configured to activatethe accumulate mode upon receiving a signal indicating an article in anexit segment for at least a predetermined length of time, wherein saidmeans for controlling the powered rollers includes means for activatingthe powered rollers to rotate in reverse to maintain the article in theexit segment.
 21. A power assisted, gravity conveyor apparatus,comprising: a frame forming a conveyor path from a first level to asecond level, a plurality of freely rotatable roller devices mounted inthe frame to provide a gravity powered conveying path, a plurality ofindividually powered rollers individually controllable to operatealternatively in a transport mode and in an accumulate mode, the poweredrollers mounted on the frame at predetermined distance intervals alongthe conveying path; means for sensing a conveyed article adjacent eachpowered roller; and control means for individually controlling a subjectpowered roller responsive to a signal from the sensing means of aconveyed article approaching said subject powered roller, wherein when asignal indicates that a powered roller immediately downstream is clearfor transport, the control means controls the subject powered roller fortransport, and when a signal indicates that a powered roller immediatelydownstream of the subject powered roller is blocked, the control meanscontrols the subject powered roller for accumulation.
 22. The conveyorapparatus as claimed in claim 21 , wherein the sensing means includes aplurality of sensors mounted on the frame, wherein one sensor is mountedadjacent to each of the powered rollers, and wherein said control meansis connected to receive signals from each of the sensors.